Sonar tow bar extension



June 6, 1961 J. B. MANUEL SONAR TOW BAR EXTENSION 5 Sheets-Sheet 1 Filed Sept. 5, 1958 Q Nu r I &M mm x N \W Mm RM w QM MW INVENTOR. M 74A4/2 BY J. B. MANUEL SONAR TOW BAR EXTENSION June 6, 1961 s Sheefs-Sheet 5 Filed Sept. 5, 1958 INVENTOR. M27566 ym/afl M. firm vA/QKS' 2,987,029 SONAR TOW BAR EXTENSION James B. Manuel, 1265 Ridge Ave., Lakewood, NJ. Filed Sept. 5, 1958, Ser. No. 759,370 2 Claims. (Cl. 114-235) (Granted under Title 35, US. Code (H52), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to tow couplings and more particularly to tow couplings for connecting flexible cables to sonar units or the like adapted to be drawn or towed through a fluid medium such as water.

Sonar or underwater detection units which are adapted to be towed by either surface vessels or airborne vehicles such as helicopters require the use of a special coupling to connect the combination towing and electrical communications cable to the housing of the sonar unit. The coupling must be capable of rigidly anchoring or connecting the tow cable to the sonar housing and in addition must provide access to the interior of the sonar housing for the electrical communications cable. Utilizing a coupling wherein the tow cable is rigidly anchored to the sonar unit, however, results in the application of bending moments to the tow cable adjacent the anchor point thereof and a consequent bending of a portion of the cable. As the sonar unit is towed through the water, the tow cable will constantly vibrate and oscillate under load and these vibrations and oscillations will result in a repeated bending and rebending of the tow cable adjacent the anchor point with the danger of an ultimate overstressing and failure of the cable.

Tow cable couplings heretofore utilized in combination with sonar units or the like have presented a serious problem of tow cable failure and loss of sonar units resulting therefrom due to the application of relatively high and destructive bending moments to the tow cable adjacent the anchor point thereof. These destructive bending moments have resulted primarily from the coupling creating a small bending radius in the portion of the tow cable undergoing bending and from the failure of the coupling to provide a means to absorb or distribute the bending stress induced therein. Due to the ever present danger of tow cable failure during a towing operation, it became necessary to periodically remove the entire sonar unit from the water and disassemble the coupling to inspect for possible breaks in the portion of the cable undergoing bending and for possible failure of the cable at the anchor point thereof. In view of the bending stresses induced in the tow cable, frequent resplicing or re-anchoring thereof became mandatory. Needless to say, the removal of the sonar unit and the disassembly of the coupling together with the frequent resplicing of the tow cable were time consuming and costly operations which required a large expenditure of man-hours and which also materially reduced the time that the sonar unit could be elfectively employed.

A tow cable coupling constructed in accordance with the present invention substantially eliminates tow cable failure due to repeated bending and consequent overstressing by providing means to increase the bending radius of the tow cable and means to distribute the stresses induced therein by bending. The tow coupling features a detachable or quick-disconnect-type locking means for anchoring the tow cable to the sonar housing and for providing access to the interior of the housing for the coaxial electrical communications cable. A rigid sleeve or bar member adapted to receive the flexible cable is carried by the locking means and functions to Patented June 6, 1961 separate by a predetermined distance the anchor point of the cable and the portion thereof undergoing bending. The rigid bar member in turn carries a resilient sleeve or cushion which surrounds the cable at the portion thereof undergoing bending. Functionally, the resilient sleeve materially increases the bending radius of the cable and the segment of the cable enclosed by the rigid sleeve provides a means to effect a reduction of the stresses in the cable clue to bending.

The nature and other advantages and applications of the present invention will be better understood by reference to the following detailed description of a preferred embodiment thereof taken in connection with the accompanying drawings, wherein:

FIG. 1 is a side elevation of the tow coupling showing an environmental application thereof;

FIG. 2 is a side elevation of the locking means of the tow coupling;

FIG. 3 is a section taken along the line III-III of FIG. 2;

FIG. 4 is a perspective view of one of the components of the tow coupling;

FIG. 5 is an exploded perspective view of the tow cou- P FIG. 6 is a top plan view of some of the components of the tow coupling; and

FIG. 7 is a section taken along the line VII-VII of FIG. 6.

Referring more particularly to the drawings, FIG. 1 shows a helicopter 10 utilized as a towing vehicle for a sonar unit 12 with a flexible coaxial tow and electrical communications cable 14 and 16, respectively, depending from the helicopter 10 and connected to the sonar unit tow by the coupling of the present invention, the coupling generally being designated by the reference numeral =18. Tow coupling 18 broadly includes a detachable locking means or lock assembly 20 for connecting the coupling to the housing of the sonar unit 12, a rigid bar member or sleeve means 22 carried by the locking means 20 and a resilient sleeve or cushion means 24 carried by the bar member 22. As will be discussed more fully hereinafter, the coaxial cable 14-16 passes through resilient sleeve 24 and bar member 22 and one end of the tow cable 14 is rigidly connected to and anchored within the locking means 20 while the electrical communications cable 16 extends beyond the locking means 20 into the interior of the sonar unit 12. A detachable fluid-tight connector 26, which per se forms no part of the present invention, is carried by the locking means 20 and completely encloses the portion of the electrical communications cable 16 extending beyond the locking means.

With the sonar unit 12 being towed, it will be noted in FIG. 1 that the coaxial cable :14-16 is deflected from the vertical by an angle A, angle A having in this instance a measurement of 8, although it will be appreciated that angle A will vary in accordance with the length of the cable between the helicopter and the coupling, i.e., the greater the distance between the helicopter and the coupling, the greater the angle of cable deflection. With cable 14-16 being deflected from the vertical and one end of the tow cable being anchored to the locking means 20, it will also be appreciated that a portion of the cable within tow coupling 18 must undergo bending and that the coupling 18 must include means to accommodate the bent portion of the cable. Resilient sleeve 24 provides the means to permit bending of the cable 14-16 and thus isfalso shown in FIG. 1 as being deflected slightly to the As best seen in FIGS. 2- -5, the locking means 20 of the coupling is comprised of a substantially cylindrical shaped body member 27 having a tapered socket or here 28 therein (FIG. 3) and provided with a counter-bore 30 in one end thereof which communicates with tapered socket 28. Counter-bore 30 in body member 27 terminates in an end wall 32 which intersects the inner end of tapered recess 28 and is also threaded at 34 to provide a means of assembling the locking means 20 to the remainder of the tow coupling components, the assembly of the coupling components to be described in detail hereinafter.

v Bodymember 27 carries a pair of opposed and laterally projecting locking lugs 36, 36 for rigidly connecting the locking means 20 to the housing of the sonar unit 12 and adjacent the locking lugs 36, 36 is provided with a pair of opposed flats or flat surfaces 38, 38 thereon (FIGS. 3 and In assembling the components of the coupling. flats 38, 38 provide a means to accommodate the reception of a wrench or the like. Body member 27 is also provided with peripheral threads 40 thereon at one end thereof for attachment of the fluid-tight connector 26 to the locking means 20.

Means is carried or receivable in tapered socket 28 of the locking means 20 to rigidly anchor the tow cable 14 to the locking means 20 and to provide a passageway to accommodate the passage of the electrical communications cable 16 through the locking means. Tow cable 14 in this instance (FIGS. 3 and 5) is a stranded two-ply cable with the strands being reversely and helically wound and with the strands of. bothplies being unwound for "a short distance adjacent the end of the tow cable. A ,tapered plug 42 having a plurality of longitudinally and circumferentially extending grooves or recesses '44 and 46, respectively, in the periphery thereof (FIG. 4) is carried in. tapered socket 28 with the unwound ends of the tow cable strands, two of which 48 and 50 are shown in FIG. 3, being seated in the longitudinal grooves 44 and ilrged into frictional engagement with the wall of the tapered socket 28. Tapered plug 42 is provided with an annular recess 52 therein adjacent the large end thereof to provide a means for splicing the tow cable strands to the plug. The tip ends 54 of the unwound tow cable strands are reversely bent to fit the contour of recess 52 and are securely held therein by a tie wire 56, although it will be apparent that any other suitable means may be utilized to secure the tip ends of the cable strands to the plug.

With the plug 42 firmly seated in tapered socket 28, as best shown in FIG. 3, the unwound tow cable strands will be rigidly anchored against movement, and the inner end of the plug 42 in combination with the intersection of tapered socket 28 and end wall 32 of counter-bore 30 will thus define an anchor point 58 for the strands of the tow cable. The entire load carried by the tow cable 14 will thus be imposed on the cable strands at anchor point 58.

In order to insure a firm and positive frictional engagement between the unwound cable strands and the wall of tapered socket 28 and the grooves 44 in plug 42 the tapered plug 42 is preferably made of a softer material than the locking means 20. In this preferred embodiment of the invention, the plug 42 is made of copper and the locking means 20 is made of stainless steel. Making the plug 42 of a softer material will enable the plug to deform to the contour of tapered socket 28 and thus insure a tight fit. The presence of both longitudinally and circumferentially extending grooves 44 and 46, respectively, in the plug 42 will further insure a tight fit of the plug by permitting a limited degree of surface deformation thereof.

Tapered plug 42 is also provided with an axially extending passage 60 therein which i adapted to accom- .modate the passage therethrough of the electrical communications cable 16. The communications cable snugly fits within passage 60 and extends beyond the plug 42 where it is received and terminates in fluid-tight connector 26 (FIG. 1), the connector 26 in this instance taking the form of a substantially cylindrical housing and being threadedly connected to the threaded end 40 of the locking means 20. In function, the connector 26 not only serves as a water-proof or fluid-tight housing for the terminal end of the communications cable 16 but also provides a means of establishing an electrical connection between the terminal end of the communications cable 16 and the electronic components (not shown) carried within the sonar housing 12.

Referring to FIGS 5-7, the rigid sleeve means or bar member 22 carried by the locking means 20 is substantially fairing-shaped and at one extremity is provided with a recess 62 therein, the recess 62 in this instance being substantially oval or elliptical-shaped and having a predetermined depth. At the opposite extremity, the bar member 22 is provided with a depending leg portion 64 which terminates in a short shank 66 having peripheral threads 68 thereon, a small shoulder 70 defining the boundary between the leg portion 64 and the shank 66. Bar member 22 is also provided with a passage 72 therein with one end of the passage terminating in oval-shaped recess 62 and the opposite end thereof terminating in shank 66. Passage 72, as best shown in FIG. 7, is adapted to accommodate the passage therethrough of coaxial cable 14-16 and at the point of intersection with elongated recess 62 defines a bending point for the cable, this bending point being designated by reference numeral 74 and hereinafter referred to as the lower bending point of the coaxial cable 14-16. I

The resilient sleeve or cushion means 24 carried by bar member 22 is also substantially fairing-shaped and is provided with a depending leg portion 76 which is adapted to snugly fit within oval-shaped recess 62. Leg portion 76 of sleeve 24 is rigidly anchored within elongated recess 62 by means of a fiat-head retaining screw 78 carried by the bar member 22 and extending through a passage 80 in leg portion 76 of the resilient sleeveJ Bar member 22 is provided with a pair of aligned passages 82 and 84 therein to receive the screw 78, passage 82 being countersunk at 85 to accommodate the bevelled head of the screw and passage 84 being threaded to re ceive the threaded shank of the screw.

Resilient sleeve 24 is provided with an elongated passage 86 therein which is adapted to register with the passage 72 in bar member 22 and thus accommodate the passage therethrough of coaxial cable 14-16. The coaxial cable snugly fits within passage 86 and any bending of the cable will result in a corresponding bending or deflection of the resilient sleeve 24. With leg portion 76 of the resilient sleeve 24 snugly fitted within oval-shaped recess 62 and with the wall of passage 86 snugly engaging the coaxial cable 14-16, it can readily be seen that the bending radius of the portion of the cable undergoing bending will be substantially increased. In this instance with the cable 14-16 being deflected from the vertical by an angle A of 8, the cable will bend between the lower bending point 74 and an upper bending point 88, the upper bending point 88 being located within passage 86 and being determined for the most part by angle A. It is also noteworthy to mention that the resilient sleeve or cushion means 24 is in this instance made of rubber although it will be obvious to those skilled in the art that any other suitable material could be utilized.

To assemble the tow coupling, the resilient sleeve 24, the bar member 22 and the body member 26 of the locking means 20 are first placed or slipped on the coaxial cable 14-16 in the order mentioned. The strands of the tow cable 14 are then unwound and the communications cable is inserted into the passage 60 in the plug member 42. The tip ends 54 of the tow cable strands are then reversely bended and the strands secured in plug recess 52. The plug 42 with the cable strands attached thereto is now tightly pulled into tapered socket 28 to rigidly anchor the cable strands to the locking means 20.

Bar member 22 is then rigidly connected to the locking means 20 by turning threaded shank 66into the threaded portion 34 of counter-bore 30, the bar 'memher 22 being turned until the shoulder 70 thereon tightly engages the end Wall 90 of the locking means 20. A wrench may be applied to the fiat surfaces 38, 38 on the locking means 20 to assist in tightly securing the bar member 22 thereto. A set screw 92 carried by the body member 27 of the locking means (FIG. 5) will, when seated, further serve to rigidly connect the two components.

After connecting the bar member 22 to the locking means 20, the assembly of the coupling components is completed by inserting the leg portion 76 of the resilient sleeve 24 into the oval-shaped recess 62 in the bar member 22 and anchoring the same therein by turning screw 78 into threaded passage 84. Before attaching the assembled coupling to the sonar unit 12, however, the communications cable 16 is first connected to the fluid-tight connector 26 and the fluid-tight connector is then connected to the threaded portion 40 of the locking means 20. The unit assembly of the tow coupling 18 and the connector 26 is then attached to the housing of the sonar unit, the locking lugs 36, 36 on the locking means 20 being adapted to be lockingly received in a pair of recesses or the like of a female adapter (not shown) carried by the sonar housing, the female adapter being well known in the art and per se forming no part of the present invention. Suffice it to say, however, that in practice one end of the female adapter is secured to the housing of the sonar unit 12 at the approximate center of gravity thereof and the other end extends to the outer surface of the housing of the sonar unit 12 where the locking lugs 36-36 on the locking means 20 can easily be inserted therein for locking engagement therewith.

In operation, as the sonar unit 12 is being towed through the Water, the coaxial cable 1416 will undergo repeated bending within the coupling between the upper and lower bending points 88 and 74, respectively, the repeated bending resulting in the application of bending stresses to the tow cable strands in addition to the stresses already applied thereto by the load of the sonar unit. Inasmuch as the bending stresses in the tow cable strands on the outside of the bend will be much greater than 1 the bending stresses on the cable strands on the inside of the bend, means must be provided to effect a reduc tion in the bending stresses in the outside cable strands in order to prevent failure or breaking of the cable.

The resilient sleeve 24 substantially reduces the bending stresses in the tow cable strands by increasing the bending radius of the portion of the tow cable undergoing bending. Instead of bending at a single point, the tow cable 14 undergoes bending between the upper and lower bending points 88 and 74, the two bending points in effect spreading the bending over a sufficient length of the cable to prevent excessively high stress concentrations in the cable strands. The rigid bar member 22 eifects a further reduction in the bending stresses by separating the anchor point 58 of the tow cable 14 and the portion thereof undergoing bending by the segment of the cable received in bar passage 72, the segment in passage 72 being operable to absorb or distribute the stresses applied to the cable between the two bending points 88 and 74. Due to the helical construction of the tow cable and the lay thereof, the cable strands at the outside of the bend between bending points 88 and 74 will be advanced or helically rotated to the reverse side of the cable one or more times before reaching the anchor point 58. The lay of the cable strands will thus allow the loads on the strands induced by bending to be substantially equalized or absorbed by the segment of the cable between the anchor point 58 and the portion of the cable undergoing bending. Tow cable 14 in this preferred embodiment of the invention has a lay of 1050 between anchor point 58 and upper bending point 88.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A tow coupling for connecting a multi-strand, flexible cable to the housing of a sonar unit adapted to be drawn through a fluid medium by a tow vehicle com prising a substantially cylindrical locking member adapted to be detachably secured to said sonar housing, said locking member having a tapered socket therein in one end thereof for receiving the unwound strands on the end of said cable and being provided with a substantially axially extending counterbore therein in the opposite end thereof intersecting said tapered socket, a tapered plug carried within said tapered socket for urging the unwound strands on the end of said cable into engagement with the Wall of said tapered socket to thereby rigidly anchor the end of said cable within said locking member, the intersection of said tapered socket and said counterbore within said locking member defining an anchor point for the end of said cable, an elongated rigid bar member connected to said locking member at said opposite end of said locking member with said bar member having a shank on one end thereof receivable within said counterbore, said bar member extending substantially longitudinally of said locking member and having a passage of predetermined length therein to accommodate the passage therethrough of said cable, said bar member having a recess therein in the end thereof opposite said shank with said recess intersecting said passage therein, the intersection of said recess and said passage in said bar member defining a bending point for said cable, and a resilient sleeve of predetermined length carried by said cable and having one end thereof received within said recess in said bar member and extending to the intersection of said recess and said passage within said bar member, said resilient sleeve being operable to extend the bending point of said cable beyond the bending point defined by the intersection of said passage and said recess in said bar member to thereby increase the bending radius of said cable when said sonar unit is being drawn through a fluid medium by a tow vehicle, said passageway in said bar member being of sutficient length to provide a segment of the cable between said anchor thereof and the portion thereof undergoing bending capable of distributing the stresses in said cable due to bendmg.

2. A tow coupling as claimed in claim 1 wherein said tapered plug is made of a softer material than said locking member and wherein said tapered plug is provided with a plurality of both longitudinally and circumferentially extending recesses in the peripheral surface thereof, the longitudinally extending recesses receiving the unwound strands on the end of said cable when said plug is received within said tapered socket in said locking member, the longitudinally and circumferentially extending recesses in the peripheral surface of said plug permitting a limited degree of surface deformation of said plug when said plug is received in said tapered socket and thereby insuring a tight fit between said plug and socket.

References Cited in the file of this patent UNITED STATES PATENTS 1,319,565 Burney Oct. 21, 1919 1,758,218 Carlson May 13, 1930 2,377,442 Ostenhoudt June 5, 1945 2,388,013 Rasor Oct. 30, 1945 2,435,956 Craig Feb. 16, 1948 2,551,596 Haglund May 8, 1951 2,673,233 Salisbury Mar. 23, 1954 FOREIGN PATENTS 666,004 Great Britain Feb. 6, 1952 

